Romney 2020?

[Mr. Morden]

Both Kasich and Romney would lose, but I think Romney has the potential to do better, and would certainly have a better shot than Kasich at winning at least one primary (Utah).

It's certainly possible for there to be enough GOP voters disenchanted with Trump in 2020 for a challenger to get Buchanan '92-esque numbers (more than 20% of the national popular vote, and more than a third of the vote in at least certain states).

But that isn't going to work if the challenger is running to Trump's left on every single issue.  You've got to pick a few issues where Trump has "let down the conservative movement" and make those central to your critique of him.  Kasich seems more likely than Romney to run to Trump's left on absolutely everything (e.g., he can't stand talking about Medicaid expansion), so I think his potential to get Buchanan '92 numbers is limited.  There just aren't enough "moderate" Republican primary voters for that to work.  Romney is more likely to take an ideological opening where he finds one, so I guess he might do OK if Trump is wounded.  But I doubt anyone can actually beat Trump for the nomination, barring some extraordinary circumstances.